Articles about Sri Lanka’s birdlife in general and the island’s bird species in particular can be found on websites of international birdwatching communities and networks.
The best way to look for lists of species occuring in a region, is simply to search wikipedia.
The following pdf-file factsheet with photos of Sri Lanka’s birds of prey is recommendable, too:
Websites and weblogs of Sri Lankan birdlovers and ornithologists are available online, too, since birdwatching and also wildlife observation are quite popular weekend and holiday activities of Sri Lankans, young people like photo excursions very much.
all Sri Lanka blog articles
by region, by topic
and A-Z here...